Personally, I don't see what's the problem with releasing .map files either. If your map is decent but boring, then who would really look at it? If your map is amazing and people want to learn, then they can take a look and learn from it. Unless you have missile launch codes in your .map, why not release it and allow people to explore? If your map has a secret, then make another version of the .map without the secret, and release the alternate version.
But meh, my opinion. Seems a lot of people are against releasing the .map source.